Alfonso I of Aragon 'the Battler' (circa 1073-1134, king of Aragon and Navarre 1104-1134). Son of Sancho I of Aragon, successor of his brother Peter I of Aragon. Conquered many places in the Ebro valley: Egea, Tudela, Zaragoza, Calatayud, Borja, Tarazona, Daroca, and Monreal del Campo. Died in September 1134 after an unsuccessful battle with the Moors at the siege of Fraga.

A passionate fighting-man (he fought twenty-nine battles against Christian or Moor), he was married in 1109 to Urraca of Castile, widow of Raymond of Burgundy, a very dissolute and passionate woman. The marriage had been arranged by Alfonso VI of Castile in 1106 to unite the two chief Christian states against the Almoravides, and to supply them with a capable military leader. But Urraca was tenacious of her right as proprietary queen and had not learnt chastity in the polygamous household of her father. Husband and wife quarrelled with the brutality of the age and came to open war. Alfonso had the support of one section of the nobles who found their account in the confusion. Being a much better soldier than any of his opponents he gained victories at Sepalveda and Fuente de la Culebra, but his only trustworthy supporters were his Aragonese, who were not numerous enough to keep down Castile and Leon. The marriage of Alfonso and Urraca was declared null by the pope, as they were third cousins.

The king quarrelled with the church, and particularly the Cistercians, almost as violently as with his wife. As he beat her, so he drove Archbishop Bernard into exile and expelled the monks of Sahagun. He was finally compelled to give way in Castile and Leon to his stepson Alfonso, son of Urraca and her first husband. The intervention of Pope Calixtus II brought about an arrangement between the old man and the young.

Alfonso the Battler won his great successes in the middle Ebro, where he expelled the Moors from Zaragoza; in the great raid of 1125, when he carried away a large part of the subject Christians from Granada, and in the south-west of France, where he had rights as king of Navarre. Three years before his death he made a will leaving his kingdom to the Templars, the Hospitallers, and the Knights of the Sepulchre, which his subjects refused to carry out. He was a fierce, violent man, a soldier and nothing else, whose piety was wholly militant. He has a great place in the reconquest.